TOA compression driver HFD-651, anyone knows?

[anubisgrau]

I'm wondering if anyone has any experience with this old TOA driver from the late 80s.

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http://www.toa-products.com/faq/siyo...65116_sa1j.pdf

I've found a system where it's loaded from 270hz on a sato horn so this driver sounds like a perfect candidate or alternative to JBL 2482 for a low mid CD solution - not many around.

homecinema-fr: Installations de passionnés

Anyone heard it or knows anyone who can shed some light on it?

I've got offered a pair with good looking diaphragms (much better than the ones above - they don't look original to me) and I'm a bit tempted though I've also sourced 2482 in a good nick. Would be good to compare them.

[elac310]

I got a pair of NOS of these drivers (8ohm versions) in a music shop almost two years ago and was intrigued enough to buy them.

In my 4 way system, all passive filtered, they now cover the range above 1800 hz with no high pass Xover (they seem to have a natural cut off also in the horn I use, i.e 18sound XR1496). Above 12kHz or so, a Beyma CP21 adds the upper higths. Onken-W type bass cover up to 350Hz, then JBL2490 w. horn 2392 from there to 1800 Hz.

The TOA has an aluminium membrane (that's why I use also an aluminium equiped Beyma tweeter). I find the sound overall smooth but it turned out to be the a difficult driver to adjust in my system; I have the feeling that the energy it deploys is considerable and geting it under control took me longer experimenting; I did use measurements both at the listening position and at close distance but a satisfactory subjective balance could only be reached by ear. Presently, I use a simple 6,8ohm resistor and then a 2,7uF cap in series. A small variation (say 5,6 or 8,2 ohms, or 3,3uF) kills the overall balance to my taste.

I haven't tried to use it as low as 270Hz; it seems a bit extreme to me for a 1,4'' driver like the TOA; besides, impedance curves of the manufacturer show a resonance frequency peak which is quite high for such a driver, at 2kHz.

For the time being, I'm quite happy with it, that is with the present horn etc.. Its resolution is definitely high; if that tells anything, when I replaced the standard MKP cap by a good tin-foil-nonmetalizedpolyprop cap, the difference was noticeable (without intellectualising...) and the new caps contribute to the qualities of the TOAs.

In fact, I also happen to have JBLs 2482 in reserve, but I haven't made comparisons so far as it would require changing completely my system (the 2482 is, I think, a true midband speaker able to cover 350 Hz to 4 or 5kHz or so in a 3 way arrangement, with an appropriate horn of course).

I would be glad to hear from your own experience, should you go for this driver. I think we are only a handful of guys out there using these vintage TOAs!

Chris.

[anubisgrau]

Thanx Chris, you have PM. Meanwhile I gave up on TOA driver as I sourced Vitavox S3 which would be a low mid driver in my next system (if I ever built it as my Summa clones works pretty decent now). I couldn't find anything about TOA and physically it looked impressive to me so I was wondering if it could go to really low mids (reaching as close to 300-ish hz as possible). Now it seems that only JBL 2482/2490 can do it relatively safely but even that I don't think it's wise to do it with a first order filter which would be one of my conditions for such an application. Thanks again for sharing your thoughts.